1. Field of the Invention
The present invention relates to an antenna, and more particularly to an antenna used for mobile communication services.
2. Description of the Related Art
With remarkable development of informalization, modern society has been developing day by day. Mobile communication systems are main means for transmitting a mass of information correctly and quickly. These mobile communication services require a variety of terminal components. Particularly, many core components like antennas for terminal device depend on imported products. Therefore, there is a keen need for development of domestic-manufactured antenna for mobile communication terminal device.
Terminal devices used for the mobile communication services are connected to duplexers to separate input and output signals each other. Typically, a compact antenna mounted on the uppermost of a terminal device is used as a final stage in a state of signal output, and is used as a start stage in a state of signal input. In this way, the antennas for mobile communication services perform a function to receive radio waves from the outside (for example, base stations, relays, or antennas attached to wireless communication devices) or transfer electric signals generated in communication devices to the outside. One of these antennas is a monopole type with a length of a quarter wavelength.
According to user's demand for good design, convenience of carrying, service commerciality in a multi-band, light weight of antennas for mobile communication, markets for portable terminal devices for mobile communication have a preference for internal antennas of the multi-band including an 800 MHz band over external antennas. In addition, according to a need for miniaturization of antennas, sizes of the antennas get smaller using a variety of structures and materials.
While Microstrip Antennas have an advantage of light weight, low profile, easiness in making into linear form or planar array, and easiness of integration into a high frequency circuit, they, have a disadvantage of narrow band characteristics, difficulty of precise polarization, and limitation of power capacity.